Magnetic frequency multiplier



March 8, 1949. H. M. HUGE 2,463,539

MAGNETI C FREQUENCY MUL'IfI PLIER Filed May 5, 1945 f 2 Sheets-Sheet l 0. c. was. I 01c. WDG.

INVENTOR. HEN/PV M HUGE M M M I TOR/V575.

Patented Mar. 8, 1949 MAGNETIC FREQUENCY MULTIPLIER Henry M. Huge, Lorain, Ohio, assignor, by mesne assignments, to Lorain Products Corporation, Lorain, Ohio, a corporation of Ohio Application May 5, 1945, Serial No. 592,095

9 Claims. 1 This invention relates to magnetic frequency multipliers and in particular to an arrangement for repeated doubling of a given input frequency by a cascade connection of magnetic frequency doublers.

Magnetic frequency changers made up of cascade-connected frequency doublers have been known for many years. In particular, such arrangements have been described by Georg Von Arcoand Alexander Meissner in U. S. Patents No. 1,181,556, No. 1,267,018 and No. 1,308,514..

Numerous difficulties have been encountered in the operation of frequency doublers in this manner, and the difficulties increase with the number of stages cascaded. One of the chief problems lies in the tendency for a voltage component .of the input frequency to appear in the output of the frequency doublers when'they are operated in cascade. Other difficulties result from the variations in tuning requirements which result from load current variations.

By my invention, both of these difficulties are overcome and it is possible to cascade a large number of frequency doubling stages and to sup- .ply a-greatly increased frequency to a variable .load such "as an induction motor.

Furthermore, my invention eliminates the need for precise tuning of the cascaded circuits and therefore facilitates the energization of variable loads.

To accomplish these results, my frequency changer utilizes a polyphase frequency changing arrangement such as that shown in my U. S. patent application Serial No. 535,480 filed May 13, 1944, now U. 5. Patent No. 2,395,389, issued February 26, 1946. In this arrangement, the outputs of frequency doublers energized from input phases 90 displaced are combined. The 90 displacement of the input voltages results in a 180 displacement at the doubled frequency and an inphase relationship at all even .harmonics of the doubled frequency. The outputs are combined so that all even harmonics of the output frequency are substantially eliminated by cancellation.

-I have found that this output voltage, which is substantially free of even harmonics, may be supplied to another frequency doubler directly without encountering the difficulties previously mentioned. There isno tendency for components of undesired lower frequencies to appear in the output of the second stage of the frequency doubler. Furthermore, if the second stage is similar to the first and the even harmonics are again eliminated, a third stage may be energized from it, and so on for additional stages until the required frequency is attained.

It is an object of my invention to obtain a large increase in frequency by a cascade arrangement of magnetic frequency doublers.

Another object of my invention is to provide a polyphase output of a greatly increased frequency.

Still another object is to eliminate components of the input frequency from the output voltage of a frequency doubler.

An additional object of my invention is to supply the biasing current for a cascade arrangement of frequency doublers from a common biasing source and to control the current in response to biasing requirements.

Other objects and a better understanding of my invention may be obtained by referring to the following specification and claims in connection with the accompanying drawings in which Figure 1 shows a three-legged saturable reactor having a center-tapped primary winding as utilized in my invention,

Figure 2 shows a second type of reactor with an untapped primary winding,

Figure 3 shows a somewhat different reactor which may be used for the same purposes as the reactors shown in Figures 1 and 2,

Figure 4 shows still another combination which may be used in place of the reactors of Figures 1 and 2, and

Figure 5 is a, schematic diagram showing how a number of reactors such as those shown in Figures 1 and 2 may be interconnected in one embodiment of my invention.

With more particular reference to Figure 1, there is shown a three-legged magnetic core structure it, having a primary winding I l on the central core member, and secondary windings l4 and l 5 with direct current windings l2 and I3 on the two outer core members. The primary winding H is provided with a center tap IT. The secondary windings l4 and I5 are phased non-inductively with respect to the primary winding I l The D. C. windings l2 and 13 are phased in the same polarity as the secondary windings.

With this arrangement, a flow of direct current produces a unidirectional flux in the two outer members of core l6. Alternating current applied to the primary winding ll produces unequal fluxes in the outer core members because of the saturating action of the unidirectional flux. The unequal division of fluxes reverses with the polarity of the primary alternating current cycle and the resultant induced secondary voltage is of twice the primary frequency.

The structureof Figure 2 is similar to the structure shown in Figure l and comprises a threelegged magnetic core 26, having primary winding 2i on its central member and secondary windings 24 and together with direct current windings 22 and 23 on its outer members. It differs from Figure 1 in that the center tap ll shown in Figure 1 is omitted in Figure 2.

In the three-legged reactor shown in Figure 3 the primary windings 34 and are wound on the two outer core members and the secondary winding 33 and the D. C. winding 32 are wound on the central core member. The primary windings are polarized noninductively with respect to the secondary winding. Direct current through the D. C. winding 32 produces unidirectional flux in the outer core members, causing the primary A. 'C. flux to divide unequally between the outer members. As described in connection with Fig ure 1, the resultant induced voltage in the secondary winding is of twice the primary frequency.

Figure 4 shows still another alternate arrange ment of frequency doubling reactors. In Figure 4, two separate transformers are used, with their primaries 36 and 31 connected in series, and secondaries and ll and also direct current windings 38 and 39 connected in series opposition with respect to the primary windings so as to be non-inductively arranged with respect to the primary. As in the arrangements of Figures 1, 2 and 3, the unequal reaction to prmary magnetization produced b the unidirectional flux in the magnetic flux paths produces an induced voltage of twice the primary frequency in the secondary circuit.

Figure 5 shows schematically the arrangement of a number of reactors of the types shown in Figures 1 and 2 in a cascade arrangement of frequency doublers for supplying a three-phase output of four times the source frequency.

The first stage of the frequency changer is shown in the upper portion of the drawing and the second stage below it. The first stage utilizes three reactors of the type shown in Figure 1 and three of the type shown in Figure 2. The first three reactors are designated A, B and C and may be considered as a first polyphase frequency doubler while the second three are designated D, E and F and may be described as a second polyphase frequency doubler.

This pair of three-phase frequency doublers is connected to the three-phase source it and the two doublers are arranged to have 90 phase displacement between their energizing voltages.

The windings in Figure 5 are designated by the same reference numbers as the corresponding windings in Figures 1 and 2. To each number there is afiiXed a letter indicating which of the reactors carries the winding in question, with each reactor designated b a letter as previously mentioned.

Interconnections of the windings in the first stage are shown diagrammatically in the upper portion of Figure 5 with th primary connections on the left side of the diagram, the D, C. connections in the center, and the secondary connections on the right side of the diagram. The positioning of the primary coils indicates the phases of the primary voltages.

The primary windings of the reactors D, E and F are energized 90 out of phase with the primaries of A, B and C. The phase displacement is accomplished as shown in Figure 5 through the use of the center taps ll on the primary windings H.

The direct current windings l2 and I3 of each frequency. Thus the secondary windings of the reactors A, B and C are connected in series and connected to the output of the rectifiers 48. Similarly the direct current windings 22 and 23 of each of the reactors D, E and F are con nected in series and connected to the rectifiers 48. The voltages in these series circuits approximately cancel each other so that they impress very little alternating current on the rectifiers 4B. In some cases it may be desirable to by-pass alternating current around the rectifiers. In such cases, capacitor '21, connected across the direct current terminals of the rectifier, is included.

The rectifiers 48 are energized from the secondaries 45, 46 and 41 of current transformers whose primary windings 42, 43 and 44 are connected in series with the input to the frequency multiplier. The current transformers may be wound on a common three-phase core and I prefer to connect the secondary windings 55, 46 and 4'! in delta as shown, in order to short-circuit the third harmonic voltage and keep down the peak inverse voltage on the rectifiers 48.

The secondary connections of the first stage of the frequency multiplier are shown in the upper right hand portion of Figure 5. In Figure 5, the secondary circuits of each two reactors whose primary circuits are energized out of phase with each other are connected in series. The windings are polarized so that the double frequency voltages appearing in the windings add together. This is possible because a 90 displacement at the fundamental frequency results in displacement at the second harmonic l4 and H; of reactor C are connected in series with the secondary windings 24 and 25 of the reactor F to supply one phase of the three-phase output. Similarly, the windings MA and MA in series with 24D and 25D supply the second phase, and MB and HR in series with 24E and 25E supply the third output phase. Figure 5 shows these output phases delta-connected, although a star connection could be used.

Capacitors 29, 30 and 3| are connected one across each of the output phases and are energized by the three-phase voltage of twice the frequency of source In. They are used to aid in the excitation of the double frequency.

As previously mentioned the 90 phase displacement between primary voltages results in a 180 displacement between secondary voltages of twice the source frequency. The phases between voltages of even multiples of twice the source frequency are even multiples of 180 or integral multiples of 360. Therefore, when the secondary windings are polarized to add voltages of twice the source frequency all even harmonics of twice the source frequency are cancelled, although odd harmonics may remain.

The second stage of the frequency multiplier is shown in the lower portion of Figure 5 and comprises three more reactors G, H and J like that shown in Figure 1 and three more reactors K, L and M like that shown in Figure 2.

The primary connections of the second stage are shown in the lower right hand portion of Figure 5, the direct currentconnections in the center and the secondary connections in the lower left hand portion of Figure 5.

The second stage of the frequency multiplier is similar to the first stage except that it does not include its own biasing source: i. e. current transformers and rectifiers. The direct current windings l2 and I3 of the reactors G, H and J are v ,c0r,1n,ected in series windings l-ZA, 13A, -.;first stage. Likewise thereactors K, Land ;M--are connected in series Lin the same manner as the windings .12 and :23 of the reactors D, E and F. "The sets of direct cur- ,rent windings are connected in parallel to the tqr zn, 3.0 d :3

t sa e mann as .in the samemanner as the i213, 4313, lzZCand RC -of the the windings "22 and 323 of output of the three-phase rectifiers 2.43. Al-

though the second stage of the multipliermight h provided with its own cur-rent transformers ,andrectifiers, the economical advantages of'the arrangement shown are obvious.

The primary windings II of the reactors G,:H and J are connected in parallel with-the capaci- -'I-he primary windings 2| of :the reactors KL and M are energized 90 out of phase with the windings H by means of the center taps [1G, HH and HJ.

The secondary windings L4, I15, 24 and,25 of thereactors G, H, J L and M are connected in the secondary windings of the reactors A, B, C, D, E and Thus, again, the even harmonics of the output voltage are eeucr d The capacitors l8, across the three phase output of four times the frequency ofsource l0 and aid in the excitation of the output voltage.

The operation of the second stage of the frequency changeris similar to that of the first stage as already described.

The common biasing arrangement produces cpmparaole biasing conditions in both the first and second stages of the frequency changer.

When a load is connected to the output of the frequency changer, its effect is reflected in the input current which flows through the primary windings 42, 43 and 44 of the current transformers; consequently, the biasing current is adjusted by the load condition. I prefer to cause the current transformers to become saturated under heavy input currents, so that the biasing currents which flow under this condition are limited-to their optimum values.

The load on the output of the second stage of the frequency multiplier may be an induction motor or other three-phase load, or it may comprise another stage of frequency multiplication, doubling or tripling as may be required. I have found that as long as the even harmonics are kept out of the Voltages, no difficulty is experienced in cascade operation of the frequency doublers, but if even harmonics appearing in the output voltage of one stage of the frequency multiplier are fed into the following stage, the difficulties mentioned earlier immediately arise. In particular, the balancing action of the reactors is described in connection with Figures 1 and 2 is no longer perfect and the secondary windings receive induced voltage of the frequency which is applied to the primary windings.

When a load which is not sensitive to the presence of even harmonics is being supplied, the last stage of the frequency multiplier may be simplified by omitting the reactors K, L and M and supplying the load with the Voltage which includes some even harmonic distortion Likewise, when a single-phase output is required, the number of reactors may be reduced.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of the parts may be made 19 and ,20 are connected without departing from the spirit-and scope of .the invention as hereinafter claimed.

I claim as my invention:

1. A frequency multiplier comprisinga plurality of cascaded frequency multiplying stages, the first stage comprising first and secondfrequency doublers, means for energizing said first doubler with an alternating voltage and means for energizing said second doubler with an alternating .voltage displaced substantially ninety degrees from the voltage energizing said first doubler, the outputvoltages of said first andsecondd l blersbeing combined and connected to a second frequency multiplying stage to supply it with an input voltage substantially free of even harmonics.

2. A frequency multiplier comprising a plurality of cascaded frequency multiplying stages, each of said cascaded stages being adaptedto be energized with voltage substantially free of-6Ven harmonics from the p-receding stage, said voltage substantially free of even harmonics being obtained from a balanced frequency doublingstage, said balanced stages each comprising .first and second frequency doublers, means for energizing said first doubler with a first alternating voltage, and means for energizing said second doubler with a voltage substantially ninety degress out of phase with said first voltage, said first and second doublers supplying output voltages with additive fundamental componentsand cancelling even harmonic components.

3 In combination with a biased-core magnetic frequency multiplier comprising a plurality of cascade-connected stages, controlled biasing means comprising a cur-rent transformer and a rectifier, said rectifier being adapted to supply biasing current tov at least two of said stages,:the primary of the current transformer being energised with the input current. to the frequency multiplier, the secondary being connected to the rectifier.

4. In combination with a biased-core magnetic frequency multiplier comprising a plurality of cascade-connected stages, controlled biasing means comp-rising a current transformer and a rectifier, said rectifier being adapted to supply biasing current to at least two of said stages, the primary of the current transformer being energized with the input current to the frequency multiplier, the secondary being connected to the rectifier, said current transformer having a magnetic core which decreases in permeability with increasing flux density within the normal range of operating flux densities.

5. A polyphase frequency multiplier adapted to be energized by a polyphase A. C. source and to supply a polyphase output, comprising in combination a plurality of cascade-connected stages, each stage comprising, in combination, saturable magnetic core means, biasing means for producing unidirectional flux in said core means, primary and secondary circuit means comprising windings on the core means, and polyphase capacitive means connected to the secondary circuit means, said primary and secondary circuit means being noninductively arranged on the core means, secondary voltage of twice the primary frequency being produced by the effect of the unidirectional flux on the saturable core means with voltage of the primary frequency being substantially balanced out of the secondary circuit means, each phase of the polyphase output being supplied from a portion of the secondary circuit means which is energized from a plurality of primary windings adapted to be energized from a plurality of primary phases which induce secondary voltage of the secondary output frequency in substantially the same phase and induce secondary voltages of even harmonics of the secondary frequency in opposing phases to substantially balance even harmonics out of the secondary output voltage.

6. In a frequency multiplier having a plurality of cascaded stages at least one of which utilizes biased magnetic core means, circuit means for supplying each of said cascaded stages with voltage substantially free of even harmonics, said circuit means comprising at least one balanced frequency doubling stage utilizing said biased magnetic core means, said balanced stage comprising a pair of frequency doublers, means for energizing one of said doublers with a first alternating voltage and means for energizing the other of said doublers with an alternating voltage substantially ninety degrees out of phase with said first voltage, said doublers supplying output voltages with additive fundamental components and cancelling even harmonic components.

7. A three-phase frequency multiplier comprising in combination a plurality of cascade-connected stages, each stage comprising, in combination, six saturable reactors each having two magnetic flux paths with primary and secondary windings thereon, the primary windings being adapted to be energized with polyphase alternating current to magnetize both magnetic fiuX paths of each reactor, the secondary windings being non-inductively wound on the two flux paths of each reactor with respect to the primary windings, biasing means adapted to produce unidirectional fiux through the flux paths causing them to react unequally to primary magnetization and thereby to induce in the secondary windings voltage of twice the source frequency, the secondary of each reactor being connected in series with the secondary of another reactor, with substantially ninety degrees phase displacement between the primary voltages of the two reactors.

8. A frequency multiplier comprising a plurality of cascaded stages in combination with biasing means for said stages, each of said stages comprising a pair of three-phase doublers adapted to operate with substantially ninety degrees phase displacement between their energizing voltages to provide in-phase outputs at twice their energizing frequency and substantially cancelling outputs at even harmonics of twice their energizing frequency, said three-phase doublers comprising saturating magnetic core means, said biasing means comprising a rectifier connected to the secondary of a transformer whose primary is connected in series with the input to said frequency multiplier.

9. A frequency multiplier comprising a plurality of cascaded stages in combination with biasing means for at least one of said stages which comprises a pair of three-phase doublers adapted to operate with substantially ninety degrees phase displacement between their energizing voltages to provide in-phase outputs at twice their energizing frequency and substantially cancelling outputs at even harmonics of twice their energizing frequency, said three-phase doublers comprising saturating magnetic core means, said biasing means comprising a rectifier connected to the secondary of a transformer whose primary is connected in series with the input to said pair of frequency doublers.

HENRY M. HUGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,597,937 Wagner Aug. 31, 1926 1,875,250 McCarty et a] Aug. 30, 1932 FOREIGN PATENTS Number Country Date 517,468 Great Britain Jan. 31, 1940 767,407 France July 17, 1934 

